Nerf Lux Ultimate Cd?

Just had a game where our lb lost lane to a lux, so I swapped with the leblanc to see if he could recover. First thing Lux does when I get into lane is ult the wave. Thought it was a waste until 20-30 secs later, she does again. Then we go to fight enemy at rift and Lux's ultimate is up for the 3rd time within a short period of time.

Yeah, enemy had 1 cloud drake but every 20-30 secs is a bit extreme for the type of ultimate Lux has. We're talking about something that can nuke teams and clear waves.

Imagine games where an enemy Lux gets 2-3 cloud drakes. She's literally going to play the game as if it's URF. Feel as if Lux's ultimate needs a nerf on the cd or cloud drakes need a massive nerf or swap back to movement speed buffs.